Filter systems are commonly used in the presence of vapors and other hazardous airborne substances. Exemplary filter systems include collective protection systems, disposable personal respirators, reusable personal respirators, powered air purifying respirators, haz-mat suits and other protective devices.
Various chemical, optical or electronic indicators have been proposed for warning users of protective devices of the presence of undesired materials. For example, an end-of-service-life indicator (“ESLI”) can warn that a filter element in such a device may be approaching saturation or may be ineffective against a particular material.
The ability to detect chemical analytes, especially organic chemical analytes, is important in many applications, including environmental monitoring and the like. Some devices that have been used for detection of chemical analytes have been developed, for example optical, gravimetric, microelectronic, mechanical, and colorimetric.